Experimental research on magnetically insulated transmission line oscillator with metal array cathode

Velvet is widely used in magnetically insulated transmission line oscillator (MILO) as emission material of cathode. However, short lifetime (usually less than 50 shorts) and large outgassing rate of velvet make it difficult to be applied in repetitively operated MILO. To find a substitution of velvet for higher performance or repetitive operation of MILO, metal array cathode is applied. This paper presents experimental research results of an L-band MILO with metal array cathode. Metal plates with different radii and thicknesses were periodically arranged in longitudinal direction on a cathode substrate to act as array emitters. To ensure stability of the tube, higher-order-mode-depressed (HD) structure^1,2 was applied. The tube was tested on a single shot low impedance pulse power system. Output parameters of both input pulse and output microwave of the tube were measured to test its performance. Experimental results revealed that HDMILO with metal array cathode works steadily at the fundamental mode. Comparison experiments were carried out with velvet cathode. Outgassing rate was obtained by pressure difference measurement after each shot. The HDMILO with metal array cathode has a same power level with velvet cathode while it has a much longer lifetime (more than 400 shots) and a much lower outgassing rate (one order of magnitude lower). This tube brings a promising approach to repetitive operation of MILO.